Port forwarding on backup internet connection

[Yourguide32]

Howdy folks, 

Well our port forwarding setup works perfectly on our primary internet connection... but upon switching to the backup internet connection it does not work.

I have tried using the dynamic hostname of the MX in my application which appears to switch to the correct IP just a few minutes after making the switch to backup internet.... yet traffic doesn't appear to be making it through via the port forward. 

Using the new external IP after switching also does not work. 

I have tried a rule that is set to "both" on the uplink, and also two rules using specific Uplinks of Internet 1 and Internet 2, but nothing is working.

[GreenMan]

Did you raise a case with Meraki Support?

[Yourguide32]

Yes sir I am working a ticket with them and plan to update this post when a resolution is found. Currently they have just had me take the 2 rules I had, one for each WAN connection and combine them to a single that applies to "both".  Which is actually the way I had it originally and doesn't work either. So waiting for next step now. 

[PhilipDAth]

Do you have the public IP address of your backup connection directly on the MX, or is it sitting behind something doing NAT?

If it is the NAT case, then they device has to also be configured to port forward to the MX WAN interface,

[Yourguide32]

Yes sir, public IP is is directly connected and not behind anything else.  Our first attempt was with a cellular provider using a Meraki cellular connection.. but that never worked so we have switched to a Starlink Internet connection (In bypass mode for those that know what that is) directly connected to the MX64. 

[PhilipDAth]

I haven't tried doing NAT of Starlink.  It's possible they don't allow inbound connections to be initiated.